
Issued December 16, 1912. 



U. S. DEPARTMENT OF AGRICULTURE. 
BUREAU OF PLANT INDUSTRY— BULLETIN NO. 265. 

B. T. GALLOWAY, Chi^ of Bureau. 



.H5 



SOME FACTORS INFLUENCING THE 

EFFICIENCY OF BORDEAUX 

MIXTURE. 



LON A. HAWKINS, 
Scientific Assistant, Frult-Disense Investigations. 




WASHINGTON: 

GOVERNMENT PRINTING OPFIOE. 

1912. 



"lonagTRpw 




Qassiur. 
Book- M2^ 



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J 4 1/ 



Issued December 16, 1912. 

U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 265. ^ 

B. T. GALLOWAY, ChieS of Bureau. 



SOiME FACTORS INFLUENCING THE 

EFFICIENCY OF BORDEAUX 

MIXTURE. 



LON A. HAWKINS, 
Scientific Assistant, Fruit-Disease Investigations. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

1912. 



'b 



^ 



.^' 






BUREAU OF PLANT INDUSTRY. 



Chief 0/ Bureau, Beverly T. Galloway. 
Assistant Chief of Bureau, William A. Taylor. 
Editor, J. E. Rockwell. 
Chief Clerk, James E. Jones. 



Fruit-Disease Investigations. 

scientific staff. 

M. B. Waite, Pathologist iti Charge. 
C. L. Shear and Charles Brooks, Pathologists. 
W. S. Ballard, Assistant Pathologist. 
John W. Roberts, S. M. McMurran, F. V. Rand, Lon A. Hawkins, George W. Keitt. W. 

Ralph Jones, D. F. Fisher, 'Clara H. Hasse, Angle M. Beckwith, Scientific Assistants. 
Leslie Pierce, Agent. 
J. Marion Shull, Expert. 
265 
2 

0^ n. 

JAN 3 1913 



LETTER OF TRANSMITTAL, 



U. S. Department of Agriciilture, 

Bureau of Plant Industry, 

Office of the Chief, 
Washington^ D. C.^ Septemher 10^ 1912. 
Sir : I have the honor to transmit herewith and to recommend for 
publication as Bulletin No. 265 of the series of this bureau a manu- 
script by Mr. Lon A. Hawkins, Scientific Assistant in Plant Pathol- 
ogy, entitled " Some Factors Influencing the Efficiency of Bordeaux 
Mixture." 

This paper, submitted by Mr. M. B. Waite, Pathologist in Charge 
of Fruit-Disease Investigations, presents the results of investigations 
of various methods of preparation of Bordeaux mixture and of the 
effect of adding to the mixture different compounds designed to in- 
crease its adhesiveness. 

The results obtained are of importance where this fungicide is 
used and should be of special interest to cranberry and grape growers. 
Respectfully, 

B. T. Galloway, 

Chief of Bureau. 
Hon. Jainies Wilson, 

Secretary of Agriculture, 

265 



CONTENTS. 



^ Page. 

Introduction 7 

Composition of Bordeaux mixture 7 

Preparation of Bordeaux mixture 8 

Experiments in preparation 10 

Effect of different methods of mixing on the rate of subsidence of the 

suspension 10 

Effect of varying amounts of agitation on the subsidence of the sus- 
pension 11 

Experiments with concentrated lime poured into dilute copper 

sulphate 11 

Experiments with concentrated copper sulphate poured into 

dilute lime 13 

Discussion of effects of agitation 13 

Adherence of Bordeaux mixture with and without added adhesives 16 

Historical review of work on adherence 16 

Experiments on adhesiveness 17 

Experiments on adhesiveness to grape leaves 18 

Experiments on adhesiveness to grape berries 20 

Surface tensions of mixtures used 21 

A laboratory method for comparing the efficiency of added adhesives. . 23 

Discussion of the results of the experiments 26 

Conclusion 28 

205 5 



ILLUSTRATIONS. 



Fig. 1. Diagram showing the effect of varying the amount of agitation of 
Bordeaux mixture when the concentrated lime is added to the 
diluted copper-sulphate solution 12 

2. Diagram showing the effect of varying the amount of agitation of 

Bordeaux mixttu-e when the concentrated copper-sulphate solution ia 
added to the diluted lime 14 

3. Sketch of apparatus used for measuring the depression of the eiuface 

films of Bordeaux mixture by the bloom of the grape 24 

4. Diagram which compares the average depressions of the surface films 

seen in the horizontal microscope of Bordeaux mixtm-e without 
added adhesive and Bordeaux mixture with 2 pounds of rosin-fishoil 
soap to 50 gallons of mixture 25 

205 

6 



B. P. 1.— 77S. 

SOME FACTORS INFLUENCING THE EFFI- 
CIENCY OF BORDEAUX MIXTURE. 



INTRODUCTION. 

The efficiency of Bordeaux mixture in preventing certain diseases 
which attack the young aerial portions of plants is dependent on 
several factors. Not the least among these is uniformity in the dis- 
tribution of the copper compound throughout the liquid medium 
when the mixture is applied. That this is of importance is very 
apparent, for if the copper compound has settled out, even to a limited 
degree, part of the plant will receive a heavy coating of the fungi- 
cide, while other portions may receive none and thus be liable to 
infection by the fungus. Another important factor is adhesiveness, 
as it is obviously necessary for the fungicide to adhere to the sus- 
ceptible portions of the plant if they are to be protected from fungous 
disease. With these requirements for efficiency in mind the questions 
naturally arise, By what methods can the most uniform distribution 
of the copper compound in the medium be obtained, and how can the 
adhesiveness of the mixture to the susceptible parts of the plants be 
increased? The present investigation deals with these two questions. 

COMPOSITION OF BORDEAUX MIXTURE. 

Bordeaux mixture is made up of copper sulphate and calcium 
hydroxid, and the rate of subsidence of the colloidal suspension of 
the precipitate which results from the interaction of these substances 
is partly dependent on the manner in which the two components are 
brought together. It is not necessary here to go into a detailed dis- 
cussion of the chemical reactions that take place when copper sulphate 
and calcium hydroxid are brought together. They have been studied 
by Swingle,^ Chester,^ Sostegni,^ Pickering,* and others, with various 

1 Swingle, Walter T. Bordeaux Mixture : Its Chemistry, Physical Properties, and Toxic 
Effects on Fungi and Algas. Bulletin 9, Division of Vegetable Physiology and Pathology, 
U. S. Dept. of Agriculture. 1896. 

2 Chester, F. D. Copper Salts as Fungicides. Journal of Mycology, vol. 6, 1890, pp. 
21-24. 

3 Sostegni, Livio. Sulla Composizione Chimica della Cosi detta Poltiglia Bordolese. Le 
Stazioni Sperimentali Agrarie Italiane, vol. 19, 1890, pp. 129-141. 

* Pickering, Spencer U. Eleventh Report of the Woburn Experimental Fruit Farm. 
1910. 

265 7 



8 FACTORS INTLUENCING EFFICIENCY OF BOEDEAUX MIXTURE. 

conclusions as to the nature of the compounds formed. It is gen- 
erally agreed that the insoluble copper compound of Bordeaux mix- 
ture, whether copper hydroxid, basic sulphate of copper, or both these 
compounds, is in colloidal suspension in a saturated or nearly satu- 
rated solution of calcium sulphate and calcium hydroxid. 

PREPARATION OF BORDEAUX MIXTURE. 

Different authors have recommended various methods for the prep- 
aration of Bordeaux mixture, with a view of obtaining the most eco- 
nomical and effective mixture. Millardet,^ in describing the making 
of Bordeaux mixture for the first time, says : 

Dans 100 litres d'eaii quelconque (de puits, de pluie, ou de riviere) on fait 
dissoudre 8 kilos de sulfate de cnivre du commerce. D'un autre cote, on fait, 
avec 30 litres d'eau et 15 kilos de chaux grasse, en pierres, un lait de chaux 
qu'on melange a la solution de sulfate de cuivre. 

This method of mixing, with the same formula, was adopted in 
America, having been first published by Scribner--^ in 1886. Two 
years later Scribner* recommended 4 pounds of copper sulphate and 
a like quantity of lime in 22 gallons of mixture, while Galloway'' 
the same year recommended a formula of 6 pounds of copper sul- 
phate and 4 pounds of stone lime to 22 gallons of water. Waite® in 
1893 obtained good results in spraying for pear leaf-blight by using 
6 pounds of copper sulphate to 50 gallons of water with just sufficient 
lime to react with the copper sulphate. In the same article this 
writer recommends the use of a stock solution of copper sulphate and 
a stock mixture of lime in the preparation of the fungicide. With 
these formulas, the method of preparation was to pour the calcium 
hydroxid into the copper-sulphate solution. In 1896 Galloway'' rec- 
ommended the use of two tubs, in which the copper sulphate and 
lime were separately diluted, each to half the volume of the Bordeaux 
mixture required. From these tubs the two solutions were poured 
simultaneously into a barrel. In the same article he recommended 

^Millardet, A. Journal d'Agriculture et d'Hortlculture de la Gironda, May 1, 1S85. 

Note. — This publication was not at hand and the quotation given was taken froni the 
same writer's paper, entitled " Sur I'histoire du traitement du mildiou par le sulfate de 
Cuivre," Journal d'Agriculture Pratique, vol. 49, pt. 2, 1885, pp. 801-805, in which Mil- 
lardet quotes directly from his former paper in describing the method of preparing 
Bordeaux mixture. 

2Scribner, F. Lamson. Report on the Mycological Section, in the Report of the Com- 
missioner of Agriculture for 1886, p. 100. 

8— Report on the Fungous Diseases of the Grapevine. Bulletin 2, Section of 

Plant Pathology, Botanical Division, U. S. Dept. of Agriculture, 1886, p. 16. 

4 Fungicides or Remedies for Plant Diseases. Circular 5, Section of Vegetable 

Pathology, Botanical Division, U. S. Dept. of Agriculture, 1888. 

B Galloway, B. T. Treatment of Black Rot of the Grape. Circular 6, Section of 
Vegetable Pathology, Botanical Division, U. S. Dept. of Agriculture, 1888, p. 2. 

«Waite, M. B. Treatment of Pear Leaf-Blight In the Orchard. Journal of Mycology, 
7, 1894, pp. 333-388. 

'Galloway, B. T. Spraying for Fruit Diseases. Farmers' Bulletin 38, U. S. Dept. of 
Agriculture, 1896, p. 6. 
265 



PREPAKATION OF BOEDEAUX MIXTURE. 9 

6 pounds of copper sulphate and 4 pounds of lime to 50 gallons of 
mixture. This last method of mixing Bordeaux has been recom- 
mended by the investigators in the Department of Agriculture and 
most of the agi'icultural experiment-station workers in the United 
States since that time. Some of the experiment stations, however, 
recommend the pouring of one component into the other, as shown 
by the publication of Woods and Hanson,^ Green, Selby, and Gos- 
sard,- and Smith and Smith.^ Kelhofer* in an account of his in- 
vestigations on the preparation of Bordeaux mixture says: 

Die grossteu Niederscliliige erzielen wir demnach bei langsamem (portionen- 
weisem) Zusatz der Kupfervitriollosimg zur Kalkmilcli. Anniihemd ebenso 
giinstige Resultate werden erhalten, wenn man die Kalkmilcti rasch zur Kupfer- 
vitriollosung giesst. 

The copper sulphate and lime of Kelhofer's preparations were both 
diluted to the same volume. Tw^o series of experiments were carried 
out, in one of which this volume was one-half that of the fungicide 
required and in the other one-fourth. Kelhofer^-*^ also added with 
good results small quantities of cane sugar to retard the rate of sub- 
sidence of the suspension. Kuliscli^ repeated some of Kelhofer's 
experiments with like results. Pickering,^ in making common Bor- 
deaux mixture, recommends the use of calcium hydroxid as dilute 
as possible to make the required quantity and the copper sulphate in 
concentrated solution. The copper sulphate is poured into the cal- 
cium hydroxid with very little stirring. An examination of the liter- 
ature of this subject shows that the methods recommended for the 
preparation of a colloidal suspension of the copper compound which 
settles out slowly are rather varied. The problem of making a sus- 
pension which subsides slowly then resolves itself into testing the 
methods of mixing recommended by the different investigators to 
determine their comparative efficiency. Accordingly, to determine 
the effect on the rate of subsidence of the suspensions of some of these 

1 Woods, Charles D., and Hansen, H. H. Paris Green Bordeaux Mixture. Bulletin 
154, Maine Agricultural Experiment Station, April, 1908. 

2 Green, W. J., Selby, A. D., and Gossard, II. A. Spray Calendar. Bulletin 232, Ohio 
Agricultural Experiment Station, 1911. 

3 Smith, R E., and Smith, Elizabeth H. Bulletin 218, Agricultural Experiment Station 
of the University of California, 1911, p. 1185. 

* Kelhofer, W. Versuch iiber die Herstellung der Bordeauxbriihe. Jahresbericht der 
Deutsch-Schweizerischen Versuchstation und Schule fiir Obst-Wein- und Gartenbau, vol. 
8, 1897-98, p. 65. 

'' Kelhofer, W. Versuche iibcr die Beeinflussung der Haltbarkeit der Bordeaubriihe 
durch Zusiitze. Jahresbericht, der Deutsch-Schweizerischen Versuchstation und Schule fiir 
Obst-Wein- und Gartenbau, vol. 9, 1898-99, pp. 87-92. 

* Ueber einigo Gesichtspunkte bei der Herstellung der Bordeauxbriihe. Zeit- 

schrift fiir Pflanzenkrankheiten, vol. 18. Intemationaler Phytopathologischer Dienst, vol. 
1, no. 3, 1908. pp. 65-73. 

' Kulisch, P. Die Darstellung haltbarer Kupferbriihen zur Bekiimpfung der Peronospora. 
Zeitschrift fiir Pflanzenkrankheiten, vol. 21, 1911, pp. 382-384. 

* Pickering, Spencer U. Op. cit., p. 56. 

61566°— Bul. 265—12 2 



10 FACTORS INFLUENCING EFFICIENCY OF BOEDEAUX MIXTURE. 

methods of preparing Bordeaux mixture the investigations described 
in the first part of this paper were planned and carried out. 

EXPERIMENTS IN PREPARATION. 

For the greater part of the investigation the copper sulphate and 
lime used were what is commonly known as chemically pure. Dis- 
tilled water was used in these preparations. Later, a number of the 
series were repeated in order to approach commercial conditions as 
closely as possible, using a good gi-ade of common stone lime, com- 
mercial copper sulphate, and tap water. The mixtures were prepared 
in glass-stoppered cylinders of 1-liter capacity graduated to divisions 
of 10 cubic centimeters. To prepare Bordeaux mixture by allowing 
the two diluted components to flow simultaneously into the container, 
two burettes of 1,000 cubic centimeters capacity were placed side by 
side, with the outlets connected by rubber tubes provided with 
pinch cocks to a single Y tube, the lower arm of which was so ar- 
ranged as to project into the neck of the glass cylinder. The proper 
quantity of calcium hydroxid, made by slacking 3.75 grams of cal- 
cium oxid, was placed in one burette and diluted to half a liter, 
while in the other was placed a solution of the same volume, con- 
taining 5 grams of copper sulphate. A current of air was forced in 
at the bottom of the burette containing the calcium hydroxid to keep 
the precipitate from settling out. If the two pinchcocks were opened 
at the same time the milk of lime and the copper-sulphate solution 
flowed simultaneously into the graduated receiver, and by properly 
manipulating the pinchcock either component could be added to the 
other. This apparatus was used in preparing all mixtures in which 
both the lime and the copper sulphate were diluted to the same vol- 
ume before bringing them together. The comparative volumes of the 
precipitates were determined by measuring the fall of the precipi- 
tate surface in the different mixtures during a given time interval, 
the graduations on the cylinders serving as convenient indexes for 
this purpose. The formula used in the preparation was usually that 
for 4-3-50 Bordeaux mixture (4 pounds of copper sulphate and 3 
pounds of lime to 50 gallons of water), which is a standard formula 
for use on grapes and cranberries. 

Effect of Different Methods of Mixing on the Eate of Subsidence of the 

Suspension. 

The methods of mixing were as follows : 

(1) Calcium hydroxid and copper sulphate were made up to 500 cubic centi- 

meters each and allowed to flow simultaneously into the receiver. 

(2) Calcium hydroxid and copper sulphate were made up to 500 cubic centi- 

meters each and calcium hydroxid allowed to flow into the copper 
sulphate. 
265 



PKEPAEATIOlSr OF BOEDEAUX MIXTURE. 11 

(3) Calcium laydroxid and copper sulphate were made up to 500 cubic centi- 

meters each and copper sulphate allowed to flow into the calcium 
hydroxid. 

(4) Calcium hydroxid was made up to 950 cubic centimeters and shaken; 

copper sulphate was made up to 50 cubic centimeters and poured into 
the calcium hydroxid. 

(5) Copper sulphate was made up to 950 cubic centimeters; calcium 

hydroxid was made up to 50 cubic centimeters and added to the 
copper sulphate. 

(6) Calcium hydroxid and copper sulphate were made up to 50 cubic centi- 

meters each ; the calcium hydroxid was added to the copper-sulphate 
solution and the mixture diluted to 1,000 cubic centimeters. 

In addition to these the rate of subsidence of Woburn Bordeaux 
mixture, recommended by Pickering, which is made from clear 
lime water and copper-sulphate solution, was tested. 

The results obtained in these tests were varied. Throughout the 
investigation, however, No. 1, the method of mixing described first by 
Galloway, was found to result in a suspension which subsided as 
slowly as any of the others, except the Woburn Bordeaux mixture. 
The results with No. 2 and No. 3 in most cases closely approached 
those with No. 1. With Nos. 4 and 5, in which one of the compo- 
nents in a concentrated form was poured into the other made up to 
nearly the volume of fungicide desired, about as good results were 
obtained as with No. 1, provided the mixtures were properly agitated. 

When the two components were brought together in concentrated 
form, as in No. 6, the suspension settled out much more rapidly than 
with any of the other preparations. This method of making Bor- 
deaux mixture seems therefore to be entirely unsatisfactory, as has 
been almost universally held by previous waiters. 

Effect of Varying Amounts of Agitation on the Subsidence of the 

Suspension. 

Experiments were carried out to test the effects of varj^ing amounts 
of agitation on the rapidity of subsidence of the suspension when 
prepared by adding one of the components in concentrated form to 
the other made up to nearly the quantity of solution required, as in 
Nos. 4 and 5. In agitating, the graduates were stoppered and shaken 
vigorously with an up-and-down motion, the amount of agitation 
being measured by the number of complete excursions made by the 
container during the shaking. As there was always a large air space 
above the liter of mixture in the graduated cylinder, a very thorough 
agitation could be easily obtained by this method. 

EXPERIMENTS WITH CONCENTRATED LIME POUTIED INTO DILUTE COPPER SULPHATE. 

In experiments with the concentrated lime poured into the dilute 
copper-sulphate solution, five mixtures were prepared: A, The stand- 
ard solution, for purposes of comparison, was mixed by allowing the 
copper sulphate and calciiun hydroxid, each diluted to 500 cubic 

265 



12 



FACTOKS INFLUENCING EFFICIENCY OF BORDEAUX MIXTURE. 



centimeters, to flow simultaneously into the 1,000 cubic centimeter 
graduate. The others, B to E, were prepared by pouring the lime, 
made up to 50 cubic centimeters, into the copper-sulphate solution 
diluted to 950 cubic centimeters. A and B were each shaken 5 times; 
(7, 15 times; Z>, 25 times; and E, 35 times. The preparations were 
then allowed to stand one hour, when the volume of the precipitate 
was read on the scale of the graduate. It was found that the pre- 



Allftft "" 



i 




Fig. 1.— Diagram showing the effect of varying the amount of agitation of Bordeaux 
mixture when the concentrated lime is added to the diluted copper-sulphate solution. 
The shaded portion represents the precipitate after 1 hour. In A, the standard solu- 
tion, the two components diluted to half the quantity were poured simultaneously 
into the container and shaken 5 times. In B, C, D, and E, the concentrated lime was 
poured into diluted copper-sulphate solution and shaken 5, 15, 25, and 35 times, respec- 
tively. 

cipitate in B, shaken the same number of times as the control, settled 
much more rapidly than A, while in C to E, shaken from 15 to 35 
times, the suspension subsided with about the same rapidity as in 
A. The experiments were repeated a number of times, with similar 
results. The average volume from three separate experiments is 
shown graphically in figure 1. A description of the treatment given 
the preparations and the results obtained are given in Table I. 

265 



PREPARATION OF BORDEAUX MIXTURE. 



13 



Table I. — Results of tests showing the effect of agitation of Bordeaux mixture 
when the concentrated lime is poured into the dilute eoppcr-sulphatc solu- 
tion. 



Mixture used and method of preparation. 




Average vol- 
ume of precip- 
itate after 1 
hour, as meas- 
ured on scale 
of the graduate. 



A . Standard, both Ca(0n)2 and CuSO^ diluted to 500 cubic centimeters 

and allowed to flow simultaneously into receiver , 

B. Ca(OH)2 diluted to 50 cubic centimeters and poured into CuSO^ solu- 

tion diluted to 950 cubic centimeters 

C. Preparation same as i? 

D. Preparation same as i? 

£!. Preparation same as B 



Cubic centi- 
meters. 

970 

805 
970 
970 
970 



EXPERIMENTS WITH CONCENTRATED COPPER SULPHATE POURED INTO DILUTE LIME. 

In the series of experiments in which the copper-sulphate solution 
was made up to 50 cubic centimeters and then poured into the lime 
made up to 950 cubic centimeters the results were much the same as 
when the concentrated calcium hydroxid was poured into the dilute 
copper sulphate. The experiments are comparable in every way, 
since in both series the same quantities were used, the gradations 
in amount of agitation were the same, and the observations were 
made after the same length of time. The individual experiments 
were repeated a number of times, with practically the same results. 
An average of three, in which the preparations were made up with 
commercial copper sulphate and common stone lime, gave the results 
as shown in Table II. 



Table II. — Results of tests showing the effect of the agitation of Bordeaux 
mixture when the concentrated copper-sulphate solution is poured into the 
dilute lime. 



Mixtiu-e used and method of preparation. 



Times 
shaken. 




Average vol- 
vime of precipi- 
tate after 1 
hour, as meas- 
ured on scale 
of the gradu- 
ate.' 



A. Standard, both Ca(OH)2and CuSOi diluted to 500 cubic centimeters 

and allowed to flow simultaneously into receiver 

B. CUSO4 diluted to 50 cubic centimeters and poured into the Ca(0H)2 

diluted to 950 cubic centimeters 

C. Preparation same as £ 

D. Preparation same as i? , 

E. Preparation same as £ 



Cubic centi- 
meters. 

972i 

703 
836 
916 
900 



1 A graphic representation of these averages is shown in figure 2. 
DISCUSSION OF EFFECTS OF AGITATION. 

The foregoing experiments seem to show that the rate of subsidence 
of the suspension in Bordeaux mixture is not entirely dependent 
ujjon the manner in which the two components are brought together, 
but is also dependent to a certain extent on the amount of agitation 

265 



14 



FACTOKS INFLUENCING EFFICIENCY OF BOEDEAUX MIXTURE. 



the mixture receives. For example, if the mixtures, in which one of 
the components in high concentration is poured into the other diluted 
to nearly the required volume, are sufficiently agitated, the resulting 
suspension will subside about as slowly as the suspension in a mixture 
prepared by the standard method recommended by Galloway. (See 
figs." 1, C^ Z>, and E^ and 2, D and E.) On the other hand, if mixtures 




Fig. 2. — ■Diagram showing the effect of varying the amount of agitation of Bordeaux 
mixture wheu the concentrated copper-sulphate solution is added to the diluted lime. 
The shaded portion represents the precipitate after 1 hour. In A, the standard solution, 
the two components diluted to half the quantity required were poured simultaneously 
into the container and shaken 5 times ; in B, C, B, and E, the concentrated copper- 
sulphate solution was poured into dilute lime and shaken 5, 15, 25, and 35 times, re- 
spectively. 

prepared in this way receive only a small amount of agitation, the 
suspension subsides much more rapidly. (See figs. 1 B^ and 2, B.) 
A probable explanation of this fact lies apparently in the structure 
of the precipitate formed when the two components of Bordeaux 
mixture are brought together. On this subject the work of Swingle ^ 
seems to be generally accepted. 

1 Swingle, Walter T. Bordeaux Mixture : Its Chemistry, Physical Properties, and Toxic 
Effects on Fungi and Algae. Bulletin 9, Division of Vegetable Physiology and Pathology, 
U. S. Dept. of Agriculture. 1896, p. 13. 
265 



PKEPAEATIOlSr OF BORDEAUX MIXTURE. 15 

This writer has shown that when calcium hydroxid and a solution 
of copper sulphate are brought together small Traube cells are 
formed, composed of a precipitation membrane of the insoluble cop- 
per compound surrounding either a drop of calcium-hydroxid solu- 
tion or a particle of the undissolved calcium hydroxid. It may be 
suggested that in the latter case the particles of calcium hydroxid 
remaining inside the precipitation membrane might weigh them down 
and make them settle out more rapidly than those in which no solid 
was present. If, however, the mixture were sharply agitated the 
precipitation membranes might be broken and the undissolved par- 
ticles of lime could settle to the bottom without taking with them 
the precipitation membranes of the copper compound. 

This explanation receives further support from the fact that when 
Bordeaux mixture is made by allowing the two dilute solutions to 
flow simultaneousl}'^ into the container, the lime being well agitated 
meanwhile, the resulting suspension subsides much less rapidly than 
a mixture in which one of the components in high concentration is 
poured into tlie other one diluted, provided the mixtures receive only 
a small amount of agitation. In the case of the two components of 
the mixture, each diluted to half the required volume, the particles 
of calcium hydroxid would be suspended in a relatively large volume 
of liquid, and the precipitation membranes in the Bordeaux mixture 
made from this milk of lime should be smaller and contain less solid 
matter to weigh them down than if the concentrated calcium hydroxid 
were added in a pasty mass to the diluted copper-sul^^hate solution. 
On the other hand, the formation of thick, heavy precipitation mem- 
branes would be much less probable when the two diluted solutions 
were brought together than if the concentrated copper-sulphate solu- 
tion were added to the diluted calcium hydroxid. 

Pickering's Woburn Bordeaux mixture, as prepared in this investi- 
gation, also furnishes further evidence in support of this explanation. 
This mixture was prepared by adding a concentrated solution of 
copper sulphate to a saturated solution of calcium hydroxid which 
had been filtered. No undissolved calcium hydroxid and at most 
only a small quantity of undissolved calcium sulphate were in the 
mixture. Consequently, there being nothing to weigh down the pre- 
cipitate, it should remain in suspension much better than the Bor- 
deaux mixture made in the usual way. The result was as expected. 
The mixture was made up and stood on the table about two months, 
being agitated from time to time. The precipitate settled out very 
slowly after each agitation and never reached the stage at which 
it was impossible to bring it into relatively uniform suspension 
throughout the whole mixture. From these facts it seems fair to 
conclude that the slow subsidence of the suspension in the experi- 
ments in which one of the components in high concentration was 

265 



16 FACTORS INFLUENCING EFFICIENCY OF BOEDEAUX MIXTURE. 

added to the other which had been diluted to nearly the required 
volume was due to the breaking up of the precipitation membranes 
and the elimination, partially at least, of the solid calcium hydroxid 
and calcium sulphate from the suspended precipitate. Lutman,^ in 
a recently jDublished account of his investigations of Bordeaux mix- 
ture, reaches much the same conclusions in regard to the settling out 
of the precipitation membranes, 

ADHEEENCE OF BORDEAUX MIXTURE V/ITH AND WITHOUT 
ADDED ADHESIVES. 

HISTORICAL, REVIEW OF WORK ON ADHERENCE. 

The fact that it is necessary for the fimgicide to adhere to the 
surface of the plant in order to protect it from disease has led to 
many investigations of the comparative adhesiveness of different 
copi^er fungicides, both with and without added adhesives. The 
effects of added adhesives have been tested on potatoes by Girard;" 
on wheat and other cereals by Galloway;^ on grapes by Perraud,* 
Guillon and Gouirand,^ Cazeneuve,® Gastine, ^ Chuard and Porchet,^ 
and others. General studies on the adhesiveness of fungicides have 
been made by Kelhofer,°~^*^ and various other writers. Some of the 
compounds used as adhesives are soap, glue, cane sugar, dried blood, 
gelatin, and colophene. The compounds used in the present investi- 
gation to increase adhesiveness have all been tried by other investi- 
gators, with somewhat varied results, Sirrine^^ in his work on 
asparagus rust recommends the use of a rosin Bordeaux mixture, 

1 Lutman, B. F. The Covering Power of the Precipitation Membranes of Bordeaux 
Mixture. Phytopathology, vol. 2, February, 1912, pp. 32-41. 

- Girard, A. Rechorches sur I'adherence aux feuilles des plantes, et notamment aux 
feuilles de la pomme de terre, des composes cuivriques, destines &. combattre leur maladies. 
Comptes Rendus de I'Academe des Sciences, vol. 114, 1892, pp. 234—236. 

2 Galloway, B. T. Experiments with Treatment of Rusts of Wheat and Other Cereals. 
Journal of Mycology, vol. 7, 1893, pp. 195-226. 

* Perraud, Joseph. Moynes d'augmenter I'adherence des bouillies cupriqnes sur les 
raisins. Journal d'Agriculture Pratique, vol. 62, pt. 2, 1898, pp. 814-816. 

s Guillon, G. M., and Gouirand, G. Sur I'adherence de rouillies cupriques utilis^es 
pour combattre les maladies eryptogamiques de la vigne. Comptes Rendus de I'Academie 
des Sciences, vol. 127, 1898, pp. 423-424. 

<■ Cazencuve, Paul. La bouillie bordelaise albumineuse. Revue de Viticulture, vol. 9, 
1898, pp. 279-280. 

■^ Gastine, G. Les preparations cupriques et leur adherence. Bulletin Mensuel de 
rOffice de Renseignements Agricoles, vol. 5, 1906, pp. 595-603. 

8 Chuard, E., and Porchet, F. L'adhdrenee des bouillies cupriques. Revue de Viticul- 
ture, vol. 24, 1905, pp. 33-37. 

» Kelhofer, W. Ueber einige Gesichtspunkte bei der Herstellung der Bordeauxbriihe. 
Zeitschrift fiir Pflanzenkrankheiten, vol. 18. Internationaler Phytopathologiscber Dienst, 
vol. 1, no. 3, 1908. pp. 65-73. 

10 Ueber die Ausfiihrung und die Ergebnisse von Haftfestigkeitsversuchen kup 

ferhaltiger Beklimpfungsmittel gegen die Peronospora. Zeitschrift fiir Pflanzenkrank- 
heiten, vol. 17, 1907, pp. 1-12. 

11 Sirrine, T. A. Spraying for Asparagus Rust. Bulletin 188, New York Agricultural 
Experiment Station, 1900. 

265 



ADHERENCE OF BOEDEAUX MIXTURE. 17 

prepared by adding to the Bordeaux mixture a soap made from rosin, 
fishoil, and potash. Chester^ used a rosin Bordeaux mixture in 
spraying grapes and asparagus, and in referring to the grape-spray- 
ing experiments says " rosin soap added to Bordeaux mixture offered 
no advantage over the plain mixture." He, however, considered it 
of value in spraying asparagus. Shear- used rosin-fishoil soap 
with good effect in spraying cranberries. Wilson and Reddick** 
used a soap in spraying grapes in 1908. In a report of their work 
they say, " The different ' stickers,' such as rosin sal soda, or fishoil 
soap, are of no practical value." Rosin-fishoil soap was used in 
grape-spraying experiments carried on by the United States Depart- 
ment of Agriculture during the years 1907 and 1908* without 
definite results. Experiments were continued in 1909,^^ however, 
and considerable benefit was ascribed to its use. Iron sulphate has 
been recommended by Selby.*"' Glue was first used by Perraud,'^ 
and has since been employed from time to time by cranberry growers. 
From the investigations hef-e mentioned it seemed probable that the 
adhesiveness of Bordeaux mixture on parts of certain plants might 
be increased by the addition of certain compounds, though from the 
varied results obtained by the different investigators the relative 
values of these adhesives were not definitely known. An investiga- 
tion was accordingly undertaken to determine, if possible, the ad- 
hesiveness of Bordeaux mixture prepared according to several 
formulas, together with the value of certain adhesive compounds. 
It v.as also considered worth while to tr}^ to find some laboratory 
method for measuring the comparative adhesiveness of these 
mixtures. 

EXPERIMENTS ON ADHESIVENESS. 

Experiments with adhesives were carried on in connection with 
spraying experiments for the control of the black-rot of the grape 
near Vineland, X. J., in the vineyard of the Vineland Grape Juice 
Co., during the season of 1910, and at Paw Paw, Mich., in the vine- 
yard of Mr. Roy L. Tuttle, in 1911. 

1 Chester, F. D. Fungous Diseases in Delaware, Part II. Treatment of Certain Plant 
Diseases. Bulletin 63, Delaware College Agricultural Experiment Station, February, 1904. 

2 Shear, C. L. Cranberry Spraying Experiments in 1905. Bulletin 100, pt. 1, Bureau 
of Plant Industry, U. S. Dept. of Agriculture. 190(5. 

3 Wilson, C. S., and Reddick. D. The Black-Rot of the Grape and Its Control. Bul- 
letin 266, Cornell University Agricultural Experiment Station. 1909. 

* Shear, C. L., Miles, George F.. and Hawkins, Lon A. The Control of Black-rot of 
Grape. Bulletin 155, Bureau of Plant Industry, U. S. Dept. of Agriculture. 1909. 

s Hawkins, Lon A. Grape-Spraying Experiments in Michigan in 1909. Circular 05. 
Bureau of Plant Industry. U. S. Dept. of Agriculture. 1910. 

Selby, A. D. Modiflcations of Bordeaux Mixture. Sixty-second Annual Report of 
Ohio State Board of Agriculture, 1907, pp. 896-898. 

^ Perraud, Joseph. Op. cit. 
265. 



18 FACTORS INFLUENCING EFFICIENCY OF BORDEAUX MIXTURE. 

Experiments on Adhesiveness to Grape Leaves. 

The mixtures used in the experiments on grape leaves were as 
follows : 

4-3-50 Bordeaux mixture. 
4-2-50 Bordeaux mixture. 
4-3-50 Bordeaux mixture witli 2 pounds of ferrous sulpbate to 50 

gallons. 
4-3-50 Bordeaux mixture with 2 pounds of rosin-fishoil soap to 50 

gallons. 

All mixtures were made up by diluting the copper sulphate and 
calcium hydroxid each to half the volume of fungicide required, and 
allowing them to flow simultaneously into the tank of the sprayer. 
The adhesives were added as follows: The fresh solution of ferrous 
sulphate was added to the diluted solution of copper sulphate, as 
recommended by Selby; the required amount of soap was dissolved 
in a small quantity of water and poured into the Bordeaux mixture 
after it had been mixed. 

A portion of a 5-year-old Concord vineyard, in which the vines 
were apparently uniform, was divided into four plats, each plat 
being sprayed with one of the mixtures mentioned. The fungicides 
were applied with a gasoline-power sprayer. Trailers, lines of 
hose with short extension rods attached so that the nozzles could be 
manipulated by hand, were used in all sprayings. Care was taken 
in the application of the fungicide to see that all the sprayed plats 
received as nearly as possible the same quantity of the fungicide 
at any one application and that it was applied under the same 
pressure. The plats were sprayed four times, and samples of the 
leaves were collected after the first application and both before and 
after each succeeding application. Other collections were made at 
intervals, as shown in Table III. 

The method of collecting these samples was as follows : From each 
plat 40 or more leaves which appeared to represent the average con- 
dition of the foliage in the plat in regard to quantity and distribution 
of the fungicide upon the leaf surfaces were collected at the same 
time. These collections were immediately taken to the laboratory, 
the petioles removed, the leaves with holes in them or other imper- 
fections discarded, and the outlines of 30 to 40 leaves traced on paper. 
The samples were then stored in large envelopes to dry. The tracings 
were filed away and the area of the leaves determined later by means 
of a planimeter or by the weighing method. By using this number 
of leaves for a sample and with this method of determining the area 
it was considered that the quantity of copper found on the leaves 
would be proportional, within a reasonable percentage of error, to 
the quantity of copper on the leaves in the entire plat. 

265 



ADHERENCE OF BORDEAUX MIXTURE. 



19 



Later the dried leaves of a sample were removed from the envelope, 
placed in a casserole, and treated with sulphuric acid to convert the 
copper on the leaves to sulphate. They were then ashed with a 
Bunsen burner. The ash was extracted with dilute sulphuric acid, 
thrown on a filter, and washed free from copper. The copper in the 
filtrate was determined electrolytically. The area of the leaves as 
found was multiplied by two to take into account both leaf surfaces, 
and the amount of metallic copper calculated per square meter of leaf 
surface. The results of the experiment are shown in Table III. 

Table III. — Results of tests shoiving the adhesiveness of Bordeaux mixtiira 
to grape leaves. The number of milligrams of metallic copper to a square 
meter of leaf surface is shown. 



Plat 
No. 


Mixture. 


Date of collection. 


May 
20. i 


June 

14.2 


June 

15.3 


June 
10." 


July 
la.ii 


July 

14.6 


July 
31.' 


Aug. 

1.8 


Aug. 
11. 


Aug. 
18. 


Aug. 
20. 


Sept. 
5. 


1 

2 


Bordeaux mixture 
(4-3-50) 

Bordeaux mixture 
(4_2-50) 


103.8 
142 

191.1 
204. 


57.7 

130.4 
149. S 


75.4 

128.4 

121.1 
143. C 


G4.0 

87.7 
90.9 


29.2 
37.1 

29.1 
C4.3 


00.8 
59.0 

68.0 
05.7 


45.6 
37.4 

29.3 
23.7 


70.5 

08.0 

75.8 
81.8 


67.4 
04.6 

64.2 
80.4 


64.3 
03.1 

55.3 
70.3 


57.8 
58.4 

50.1 
62.3 


10.8 
35.8 


3 

4 


Bordeaux mixture 
(4-3-50) + ferrous 
sulphate 

Bordeaux mixture 
(4-3-50) + soap.... 


40.9 
40.6 



1 After first application. 
5 Before second application, 
s Alter second application. 



■> Next day after a rain, 
s Before tliird application. 
6 After third application. 



' Before fourtli application. 
8 After fourth application. 



From Table III it is apparent that there was no considerable varia- 
tion in the adhesiveness of the different mixtures throughout the 
season, though usually a little more copper per unit area was found 
on the samples of leavas from the plat sprayed with Bordeaux mix- 
ture to which the rosin-fishoil soap had been added. Immediately 
after the first application the increased adhesiveness of the rosin- 
fishoil soap mixture is very marked, but in samples collected after 
the third application a little more copper per unit area was found 
on samples from some of the other plats. On the whole, however, 
the addition of rosin-fishoil soap may be said to be of some slight 
benefit in increasing the adhesiveness of Bordeaux mixture to gTape 
leaves. 

It is apparent that in some cases the quantity of copper on the 
leaves after spraying was less than that found on the sample col- 
lected just before the same application, as before and after the second 
application in the plat sprayed with the ferrous-sulphate mixture. 
This is due to the fact that collections before spraying were made 
only of the leaves which had been sprayed in the previous applica- 
tion, while in collections made after an application leaves of all 
stages of gTOwth were collected. 

265 



20 FACTORS INFLUENCING EFFICIENCY OF BORDEAUX MIXTURE. 

Some data on the effect of a rain on the adhesiveness of the spray 
mixture are given under the dates June 15 and 16 in Table III. 
The usual collection of leaves was made immediately after the second 
spraying, and about three hours after this application rain fell, the 
precipitation being 0.71 inch. Leaves were collected the following 
day, and from these samples the results under date of June 16 were 
obtained. The amount of copper on the leaves decreased 35 to 50 
per cent by reason of the growth of the leaves during 18 hours and 
the removal of the copper by the rain. Data for plat 1 are unfor- 
tunately lacking. 

No evidence is found in these experiments to verify Kelhofer's^ 
suggestion that Bordeaux mixture with a large excess of lime adheres 
to the leaves for a longer time than the more nearly neutral mixture. 
The percentage of copper removed from the leaves in a given time 
after spraying with the 4-2-50 or 4-3-50 Bordeaux mixture varies 
only slightly. The growth of the leaves increasing the leaf area 
makes it impossible to secure accurate data on the quantity of copper 
actually removed from the leaves, but as the vines in these plats were 
the same to all appearances and the same method of sampling was 
used it is probable that the results are comparable. 

Experiments on Adhesiveness to Grape Berries. 

It was observed in the course of the preceding experiment that 
while all the mixtures adhered fairly well to the leaves there was 
considerable difference in their adhesiveness to the grape berry if 
the berry was covered with bloom. In spots on the berry from which 
the bloom had been removed, however, there seemed to be no marked 
difference in the quantity of fungicide present. When the gi'apes 
covered with this bloom were treated with Bordeaux mixture to which 
no adhesive compounds had been added the mixture seemed to run 
off immediately or round up into little droplets and hang at the 
lowest point of the fruit.- On the other hand, if the rosin-fishoil 
soap had been added, the mixture formed a film, completely covering 
the berry. From these observations it was concluded that the ad- 
herence of a fungicide to the leaves was no guaranty of its adherence 
to the fruit. In order to get accurate data upon the subject it was 
necessary to carry the experiments further, paying special attention 
to the fruit. 

This investigation on the adhesiveness of the fungicide to the 
grape berries was carried on at Paw Paw, Mich., in 1911. More 

1 Kelhofer, W. Ueber einige Gesichtspunkte bel der Herstellung der Bordeauxbriihe, 
Zeitschrift fiir Pflanzenkrankbeiten, vol. 18. Internationaler Phytopatholigischer Dienst, 
vol. 1, no. 3, 1908, pp. 6.5-73. 

" Perraud, op. cit., p. 815, noticed this difference in the adhesiveness of Bordeaux mix- 
ture on the leaves and berries in his investigations and remarks, " La faculty d'adherence 
des bouillies cupriques est beaucoup plus faible pour Ics raisins que pour les feuilles de 
vigne." 

265 



ADHERENCE OF BORDEAUX MIXTURE. 21 

adhesive compounds were used in this experiment than in that with 
the leaves, and the concentration of some of the adhesives was varied.- 
Eight plats of Concord grapes were sprayed four times in the ex- 
periment with the following mixtures : 

Plat 1 4-3-50 Bordeaux mixture. 

2. 4-3-50 Bordeaux mixture, with 2 pounds of ferrous sulphate. 

3. 4—2-50 Bordeaux mixture. 

4. 4-2-50 Bordeaux mixture, with 2 pounds of rosin-fishoil soap. 

5. 4-2-50 Bordeaux mixture, with 1 pound of rosin-fishoil soap. 

6. 4-2-50 Bordeaux mixture, with 2 pounds of flshoil soap. 

7. 4-2-50 Bordeaux mixture, with 2 pounds of ground glue. 

8. 8-2-50 Bordeaux mixture, with 2 pounds of rosin-flshoil soap. 

The soap and the ferrous-sulphate mixtures were prepared as in 
the experiment already described, and the glue (a dry, ground glue) 
was dissolved in a small quantity of hot water and added to the 
Bordeaux mixture. The mixture was prepared as in the preceding 
experiment. 

The mixtures were applied with a steam sprayer, and, as in the 
work in 1910, care was taken to see that as nearly as possible the 
same quantity of mixture was applied under the same pressure to 
each plat. Collections of grape berries were made from each plat 
immediately after the last spraying, a similar system of sampling 
being employed as in the experiment with leaves the preceding 
year. In this case, however, duplicate samples were collected from 
each plat. Each sample consisted of about 500 grapes, which were 
cut from the pedicels, the diameter measured to tenths of a milli- 
meter, and the berries stored to dry. The total area of the grape 
surfaces in each sample was calculated from the diameters of the 
individual grapes, as the berries were approximately spherical. 
Later, the copper on the grapes was determined, as in the preced- 
ing experiment with the leaves, and related to the square-meter 
grape surface for each sample. Through an accident in ashing, the 
data for one sample from plat 7 tire lacking. A second collection 
was made five weeks after the first and treated in the same way. 
The quantity of copper on the individual samples was so small in 
this case that it was impracticable to attempt to compare the data 
from the different plats. Three milligrams was the greatest weight 
of coj)per found on any sample in this last series. The weight of 
copper on grapes immediately after the fourth application is shown 
in Table IV under " Weight of copper," etc. 

SURFACE TENSIONS OF MIXTURES USED. 

In the course of the experiment on the leaves it was found that 
the mixtures with the lowest surface tension seemed to adhere best 
to the fruit, i. e., the Bordeaux mixture to which the rosin-fishoil 
soap had been added, thereby lowering the surface tension, seemed 
to adhere much more tenaciously to the bloom-covered fruit than 

265 



22 FACTOKS IITFLITENCIN-G EFFICIENCY OF BORDEAUX MIXTURE. 

the mixture without the added adhesive. This is in accordance with 
the results of the work of Vermorel and Dantony ^ on the adhesive- 
ness of certain fungicides to grape berries. These authors found 
in their investigations that the avldition of soap to the mixture 
lowered the surface tension, and that the mixture with the lowest 
surface tension wet the grape berries best. 

With a view to discovering any existing relation between the sur- 
face tension of the mixture and its adhesiveness to the bloom-covered 
grape, surface-tension measurements were made of all the mixtures 
used in the experiments in 1911. For these measurements a spring 
balance of the Joly type, provided with a loop of 36-gauge German- 
silver wire, was used. This loop consisted of a piece of wire with 
both ends bent down at right angles to the straight middle portion, 
wdiich was about 5 centimeters long. When in use, the middle portion 
of the loop was parallel to the surface of the liquid, the ends being 
perpendicular to this surface and extending below it. To determine 
the surface tension of a mixture the loop was first weighed with the 
ends thnist into the liquid and the middle portion at a given height, 
usually about 8 millimeters above the surface. The loop was then 
dipped into the liquid and weighed again with a film of the liquid 
held in the loop. The difference in weight with and without this 
film was considered to be the weight of the film. 

While taking these measurements the fungicide was contained in 
a crystallizing dish of convenient size on the stand of the apparatus. 
As the same loop was used in all measurements and at the same 
height above the surface of the liquid in each test, these weights 
should have the same relation to each other as the surface tensions 
of the liquids. The weights for samples of the Bordeaux mixtures 
used in spraying the different plats are given in column 4 of Table 
IV. The measurements are, of course, not of the highest degree of 
accuracy, yet they were made at nearly the same time, at the same 
temperature, and with all other conditions as nearly alike as possible, 
and should therefore be comparable. 

If the increased adhesiveness of the fungicide to the bloom of the 
grape is due to the lowering of the surface tension of the liquid, as 
might seem to be the case from the results obtained in 1910 in this 
investigation and from the w^ork of Vermorel and Dantony, the 
surface tensions should be inversely proportional to the adhesiveness 
of the Bordeaux mixture found by determining the copper on the 
gTape berries. From Table IV it may readily be seen that such is 
not the case. No. 4, in which 2 pounds of rosin-fishoil soap were 
added to the mixture, adhered best and had the lowest surface ten- 
sion, while in No. 5, where half the quantity of the same soap was 

1 Vermorel and Dantony. Sur les bouillies anticryptogamiques mouillantes. Reveu 
de Viticulture, vol. 35, 1911, pp. 493-494. 
265 



ADHERENCE OF BORDEAUX MIXTURE. 23 

used and which had practically the same surface tension, the quan- 
tity of copper on the berries was about two-thirds that found in 
No. 4. No. 6, in which 2 pounds of fishoil soap was added to the 
Bordeaux mixture, had the next lowest surface tension, but only 
about one-fourth as much copper to the unit area was found on the 
berries as in No. 4. No. 7, the glue mixture, which had the highest 
surface tension of any of the mixtures to which adhesives were added, 
except No. 3, most nearly approached No. 4 in adhesiveness. As may 
be seen from Table IV, no increased adhesiveness of the fimgicide 
resulted from the addition of ferrous sulphate. In the samples of 
grapes from the plat sprayed with this mixture, as well as those 
from the two plats on which Bordeaux mixtures without added ad- 
hesives were used, there was not suflficient copper present for accurate 
determination. The results of these experiments show clearly that 
the adhesiveness of the spray mixtures is not to be related directly 
to the depression of their surface tensions,^ but that some other factor 
must be taken into account. 
A Laboratory Method for Comparing the Efficiency of Added Adhesives. 

In the method used for measuring the surface tension of the mix- 
tures a surface was employed which was wet by the liquid, while the 
waxy coating of the grape under usual conditions is not wetted by 
ordinary Bordeaux mixture. Experiments to prove this point were 
made by weighing grapes covered with bloom and dipping them into 
Bordeaux mixture to which no adhesives had been added and again 
immediately weighing them. In hundreds of tests the weights before 
and after the immersion did not vary as much as a milligram. But 
when grapes were immersed in Bordeaux mixture to which 2 pounds 
of rosin-fishoil soap to 50 gallons of mixture had been added, a film 
of the liquid was formed over the surface in every case and the weight 
was increased 26 to 80 milligrams by the mixture adhering to the 
surface. 

From these experiments a method of measuring the relation of the 
liquid to the bloom of the grape itself was suggested. Strips of 
grape skin 2 to 3 millimeters in width and 20 to 40 millimeters in 
length were cut from the surface of the grapes. "V\Tien these were 
peeled off they immediately rolled up in a comparatively straight rod 
about a millimeter in diameter, with the external surface of skin on 
the outside. This rod was thrust into the mixture to be tested, which 
was contained in a crystallizing dish on a convenient stand, and the 
depression of the surface of the liquid next to the rod was measured 
by means of a horizontal microscope with a micrometer ocular. 

1 Some months after this manuscript was submitted for publication, an article by 
Vermorel and Dantony came to the writer's notice, in which they reach the conclusioli 
that the wetting power of a mixture is not related directly to the lowering of the surface 
tension. (See Vermorel, V., and Dantony, E., " Tension superficielle et pouvoir mouillant 
aes insecticides et fongicides," Revue de Viticulture, vol. 37, 1912, pp. 715-716.) 

265 



24 



FACTORS INFLUENCING EFFICIENCY OF BOEDEAUX MIXTURE. 



A series of such measurements of Bordeaux mixture with and with- 
out the added adhesives was made, and it was found that the measure- 
ments related in a rough way to the amount of copper found in the 
determination of the copper on the grapes. That is, the mixture 
which adheres best to the surface of the grape is depressed the least 
and that which adheres least is depressed the most. The other mix- 




FiG. 3. — Sketch of apparatus used for measuring the depi-ession of the surface films of 
Bordeaux mixture by the bloom of the grape. A, Source of light (Welsbach lampj ; 
B, crystallizing dish containing mixture on apparatus stand ; C, cover-glass forceps 
for holding roll of grape skin ; D, roll of grape skin thrust partly below surface of 
liquid ; E, horizontal microscope. The roll of grape skin D is placed so that the long 
axis is perpendicular to the liquid surface and the roll extends a little below this sur- 
face. The depression of the liquid surface next to the grape skin is then measured 
with the micrometer eyepiece of the horizontal microscope. 

tures with added adhesives are grouped between these two extremes 
in the order of their value as determined by the amount of copper 
on the grapes. The method of measuring this depression is illus- 
trated in figure 3. The average o:** a large number of measurements 
of Bordeaux mixture without added adhesives and with the four 
adhesives which proved of value are shown in Table IV under " De- 

265 



ADHERENCE OF BORDEAUX MIXTURE. 



25 



pression of surface of mixture." A diagram of the comparative 
depression of mixtures with the 2 pounds of rosin-fishoil soap and 
without additional adhesives is shown in figure 4. In making the 




Fig. 4. — Diagram which compares the average depressions as seen in horizontal micro- 
scope of the surface films of Bordeaux mixture without added adhesive and Bordeaux 
mixture with 2 pounds of rosin-fishoil soap to 50 gallons of mixture. X, Median line 
of eyepiece micrometer which coincides with the surface of the mixture in crystallizing 
dish ; y, graduated scale of micrometer eyepiece ; A, average depression of surface film 
of 4—2-50 Bordeaux mixture without added adhesives by the bloom of the grape ; 
B, average depression of surface film of 4-2-50 Bordeaux mixture with 2 pounds of 
rosin-fishoil soap to 50 gallons of mixture. 

measurements given in Table IV the mixture was alwaj's well agi- 
tated beforehand to stir up the precipitate and break up the film of 
calcium carbonate w^hich formed on the surface. 



Table IV. — Results of tests shoioing the adhesiveness of Bordeaux mixture 
to grape berries alone and with various added adhesives, as shoicn by 
the quantity of copper on the berries, the eomparativc surface tension of 
various mixtures used as found by weight of a film of the mixture, and the 
depression of the surface of the mixture by the bloom of the grape. 



Plat 
No. 


Mixture. 


Weight of copper to a square meter 
of grape surface. 


Weight of 

loop of 

mixture. 


Depression 
of surface 


Sample A. 


Sample B. 


Average. 


of mixture. 


1 


4-3-50 Bordeaux mixture 


Milligrams. 
Trace. 

Trace. 
Trace. 

24.5 

18.9 

5.6 

19.9 

14.7 


Milligrams- 
Trace. 

Trace. 
Trace. 

30.3 

16.4 

7.6 


Milligrams. 


^filligrams. 
726 

731 

737 

499 
490 
593 
691 

488 


Millimfter. 


2 


4-3-50 Bordeaux mi.xture with 2 

pounds of ferrous sulphate 

4-2-50 Bordeaux mixture 






3 




0. 9442 


4 

.1 

6 


4-2-50 Bordeaux mixture with 2 
pomids of rosin-fishoil soap 

4-2-50 Bordeaux mixture with 1 
pound of rosiu-fl.shoil soap 

4-2-50 Bordeaux mixture with 2 
pounds of fish oil soap 


27.4 
17.05 
6.6 
19.9 
13.85 


.4980 
.6260 
.6691 


7 


4-2-50 Bordeaux mixture with 2 
pounds of cround glue 


.6002 


8 


3-2-50 Bordeaux mixture with 2 
pounds of rosin-flslioil soap 


13.2 









205 



26 FACTORS INFLUENCING EFFICIENCY OF BORDEAUX MIXTURE. 

DISCUSSION OF THE RESULTS OF THE EXPERIMENTS. 

The results of the experiments in preparing Bordeaux mixture de- 
tailed in the foregoing pages show that the rate of subsidence of the 
suspension is not dependent on the way in which the two com- 
ponents are brought together, provided one is dilute. It should be 
possible in practice to place the proper quantity of copper-sulphate 
solution or lime paste in the spray tank, dilute it with Avater to nearly 
the quantity of fungicide desired, and then to add the other com- 
ponent in a concentrated form. By vigorous agitation this should, 
according to the experiments described here, furnish a suspension 
which settles out as slowly as in any other common method of 
preparation. (See figs. 1 and 2 and Tables I and II.) This method 
of preparation should be useful in spraying cranberries. The condi- 
tions in this w^ork are frequently such as to make impracticable the 
erection of raised platforms for mixing. It must be remembered 
that, with this method of mixing, good results were obtained only 
when the mixture was thoroughly agitated. The agitation was 
much more vigorous in the laboratory experiments than is usually 
obtained with the common barrel-pump outfit. 

The addition of cane sugar to Bordeaux mixture to decrease the 
rate of subsidence, as Kelhofer and Kulisch suggested, was not tested. 
As these writers point out, it would probably be useful under certain 
conditions for persons using a small quantity of Bordeaux mixture 
from time to time. However, in commercial work in which Bor- 
deaux mixture can be conveniently prepared and used immediately 
the addition of sugar Vv'ould seem to entail an unnecessary expense. 
The method suggested by Pickering of preparing Bordeaux mixture 
by mixing the copper sulphate solution with a saturated solution of 
calcium hydroxid makes a suspension of the copper compound which 
settles out very slov/ly. It is doubtful whether this method would 
be practicable in the preparation of the large quantities of fungicides 
required for spraying in a commercial way. It would be impossible 
to prepare a neutral Bordeaux mixture containing three-fourths to 1 
per cent of copper sulphate by this method, as a saturated solution of 
calcium hydroxid does not contain enough lime to react with the 
amount of copper salt in a solution of this concentration. The mix- 
ture might be prepared and the precipitate allowed to settle and 
enough of the supernatant liquid drawn off to leave a mixture of the 
proper concentration. This process would of course add greatly to the 
cost of spraying. It is possible that a smaller percentage of copper 
sulphate might be as effective as three-fourth to 1 per cent. From 
the evidence at hand, however, this conclusion would hardly be 
warranted. 

265 



DISCUSSION OP THE RESULTS OF THE EXPERIMENTS. 27 

Of the adhesive compounds added to Bordeaux mixture, the rosin- 
fishoil soap proved to be most effective on the grape beiTies — much 
more effective, in fact, than fishoil soap without the rosin. From this 
fact it seems probable that the adhesiveness is largely due to the 
rosin present. It is stated by various writers that the addition of a 
small quantity of soap to Bordeaux mixture could be of no particu- 
lar benefit, as the soap would be precipitated as an insoluble calcium 
soap by the excess of calcium present in the mixture. Good results 
could therefore be expected only when a considerable quantity of 
soap was added. This, of course, may be true of certain kinds of 
soap, but in this investigation considerable benefit was derived from 
the addition of relatively small quantities of soap. Even the fishoil 
soap materially increased the adhesiveness over Bordeaux mixture 
without added adhesives. 

In the treatment of the black-rot of the grape good results have 
been obtained in many cases by using Bordeaux mixture without 
added adhesives. When we consider this fact in connection with the 
evidence brought forth in the present investigation, that Bordeaux 
mixture without added adhesives does not adhere to the grape berry 
in any appreciable quantity, it seems probable that the protection is 
due to reducing the sources from which infection comes to the berry. 
By protecting the foliage from infection the possibility of secondary 
infection from the foliage to the fruit may be eliminated to a consid- 
erable extent. Covering the stems of bunches of grapes with the 
fimgicide seems to be another means by which infection may be kept 
from the grapes. The writer has observed numerous instances of 
black-rot infection on bunches of grapes which had been bagged six 
weeks or more. In these instances spores probably washed down the 
stems in drops of water, as the only openings in the bags were imme- 
diately around the stems. 

Though good results were obtained by the addition of glue to 
Bordeaux mixture, its cost (about 12 cents a pound) prohibits its 
use in commercial work in place of rosin-fishoil soap. When glue is 
added to alkaline Bordeaux mixture, part of the copper combines 
with the glue, forming a soluble compound bright purple in color. 
It is probable that much of the copper found on the grapes from this 
plat was in this form. As it is soluble in water, this protective 
covering might not remain on the berries as long as the insoluble 
precipitates in the mixtures with the soap. 

It is difficult to see in just what way ferrous sulphate could be 
expected to influence the adhesiveness of Bordeaux mixture. On 
the addition of this compound to a solution of calcium hydroxid, 
ferrous hydroxid immediately precipitates out, and none of the 

265 



28 FACTORS INFLUENCING EFFICIENCY OF BORDEAUX MIXTURE. 

ferrous sulphate remains in solution. It was found to be worthless 
as an adhesive for use on grapes. 

In the plats sprayed with 3-2-50 Bordeaux mixture, to which was 
added 2 pounds of rosin-fishoil soap, a considerable quantity of cop- 
per was found on the grapes. This formula has given excellent 
practical result and should prove much more effective than the 
mixtures containing more copper but without the adhesive. 

CONCLUSION. 

It has been shown in these investigations that a Bordeaux mixture 
in which the suspension of the copper compound settles out slowly 
may be prepared by adding the concentrated calcium hydroxid to 
the diluted copper-sulphate solution or vice versa, provided the mix- 
ture is sufficiently agitated. Practically as good results were ob- 
tained with these methods of preparation as by diluting the two com- 
ponents in separate vessels and pouring them simultaneously into a 
third, as recommended by Galloway in 1896. 

It is to be remembered that in preparing Bordeaux mixture, by 
pouring one of the components in concentrated form into the other 
diluted to nearly the required volume, the resulting mixture must be 
thoroughly agitated. The agitation necessary for preparing Bor- 
deaux mixture with a low rate of subsidence by this method could 
hardly be obtained in practice except by means of a power outfit 
provided with a good agitator. This method of mixing is not de- 
signed to replace the old gravity method with its elevated platform, 
but offers a convenient substitute where for any reason the gravity 
method is impracticable. 

In the experiments on the adhesiveness of certain Bordeaux mix- 
tures and the relative value of certain adhesive compounds it was 
shown that by determining the quantity of copper retained on the 
leaves sprayed with the different mixtures the addition of rosin- 
fishoil soap slightly increases the adhesiveness of the mixture. In 
similar experiments on grape berries it was shown that the adhesive- 
ness of the fungicide could be materially increased by the addition 
of certain adhesive compounds. Two pounds of rosin-fishoil soap 
to 50 gallons of spray mixture was the most valuable of any added 
adhesive, ground glue was second, 1 pound of rosin-fishoil soap to 
50 gallons of mixture was third, and fishoil soap was fourth. Fer- 
rous sulphate did not increase the adhesiveness of the Bordeaux mix- 
ture, as no appreciable quantity of copper adhered to the grape 
berries where the Bordeaux mixture to which the ferrous sulphate 
had been added was used. No appreciable quantity of copper was 
found on the grape berries from the plats sprayed with Bordeaux 
mixture without added adhesives. From the experiments on grape 

265 



CONCLUSION. 29 

berries with adhesives it may be concluded that the use of an adhesive 
compound is necessary to make the fungicide adhere to the bloom- 
covered grapes. Two pounds of rosin-fishoil soap to 50 gallons of 
mixture gives the best results and is recommended as the most eco- 
nomical and efficient adhesive for use on grape berries. From the re- 
sults obtained with 3-2-50 Bordeaux mixture, with the addition of 
soap, it seems probable that a mixture containing this quantity of 
copper sulphate would be effective when a good adhesive is used. A 
laboratory method of approximating the relative adhesiveness of 
these fungicides to grapes was developed. 

265 

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